This article introduces how Clickhouse monitoring works, and how to apply this monitoring on the resource

Introduction

ClickHouse is an open-source column-oriented DBMS (columnar database management system) for online analytical processing (OLAP) that allows users to generate analytical reports using SQL queries in real-time.

Pre-requisites

To configure the changes for ClickHouse monitoring you should:

  • Create User
    • CREATE USER ‘< Username >’ IDENTIFIED WITH sha256_password BY ‘< Password >';
  • Create Role
    • CREATE ROLE ‘< role >’
  • Grant minimum privileges for monitoring needs to Role and grant it to the User
    1. GRANT SELECT ON system.* TO < role >
    2. GRANT < role > to ‘< Username >’
  • Use this USERNAME and PASSWORD, and Role for Clickhouse monitoring.

Apply Clickhouse Monitoring

To apply a Clickhouse Monitoring:

  1. From All Clients, select a client.
  2. Go to Infrastructure > Resources.
  3. From the available resources, select the required resource.
  4. Select the monitor and from the Templates screen, click +Assign Templates, which displays the Apply Templates screen:
Linux Install Integration
  1. From Select Templates > Available templates, select clickhouse (v1) template. Selected templates display the chosen templates.
    Note: Select the Collector Type as Agent.

  2. Click Assign, which displays the Enter Configurations section.

Linux Install Integration
Linux Install Integration
  1. Enter Value for the Assigned Templates and Configuration Parameters and click Assign.
    Note: In the case of docker, input the ip address with the container ip address.
Linux Install Integration

The templates screen displays the selected templates.

Supported Metrics

Monitor NameDisplay NameUnits
clickhouse_ActiveAsyncDrainedConnections

Number of active connections drained asynchronously
Active Async Drained Connections,connection
clickhouse_ActiveSyncDrainedConnections

Number of active connections drained synchronously
Active Sync Drained Connections,connection
clickhouse_AsyncDrainedConnections

Number of connections drained asynchronously
Async Drained Connections,connection
clickhouse_BackgroundBufferFlushSchedulePoolTask

Number of active tasks in BackgroundBufferFlushSchedulePool. This pool is used for periodic Buffer flushes
Background Buffer Flush Schedule Pool Task,task
clickhouse_BackgroundDistributedSchedulePoolTask

Number of active tasks in BackgroundDistributedSchedulePool. This pool is used for distributed sends that are done in the background.
Background Distributed Schedule Pool Task,task
clickhouse_BackgroundFetchesPoolTask

Number of active fetches in an associated background pool
Background Fetches Pool Task,task
clickhouse_BackgroundMessageBrokerSchedulePoolTask

Number of active tasks in BackgroundProcessingPool for message streaming
Background Message Broker Schedule Pool Task,task
clickhouse_BackgroundMovePoolTask

Number of active tasks in BackgroundProcessingPool for moves
Background Move Pool Task,task
clickhouse_BackgroundSchedulePoolTask

Number of active tasks in BackgroundSchedulePool. This pool is used for periodic ReplicatedMergeTree tasks, like cleaning old data parts, altering data parts, replica re-initialization, etc.
Background Schedule Pool Task,task
clickhouse_BrokenDistributedFilesToInsert

Number of files for asynchronous insertion into Distributed tables that has been marked as broken. This metric will starts from 0 on start. Number of files for every shard is summed.
Broken Distributed Files To Insert,file
clickhouse_CacheDictionaryUpdateQueueBatches

Number of 'batches' (a set of keys) in update queue in CacheDictionaries
Cache Dictionary Update Queue Batches
clickhouse_CacheDictionaryUpdateQueueKeys

Exact number of keys in update queue in CacheDictionaries.
Cache Dictionary Update Queue Keys,key
clickhouse_ContextLockWait

Number of threads waiting for lock in Context.
Note: This is a global lock.
Context Lock Wait,thread
clickhouse_Systemmetric_DelayedInserts

Number of times the INSERT of a block to a MergeTree table was throttled due to the high number of active data parts for partition.
Systemmetric Delayed Inserts
clickhouse_DictCacheRequests

Number of requests in fly to data sources of dictionaries of cache type.
Dict Cache Requests,request
clickhouse_DiskSpaceReservedForMerge

Disk space reserved for currently running background merges. It is slightly more than the total size of currently merging parts.
Disk Space Reserved For Merge,byte
clickhouse_DistributedFilesToInsert

Number of pending files to process for asynchronous insertion into Distributed tables. Number of files for every shard is summed.
Distributed Files To Insert,file
clickhouse_DistributedSend

Number of connections to remote servers sending data that was INSERTed into Distributed tables. Both synchronous and asynchronous mode.
Distributed Send,connection
clickhouse_EphemeralNode

Number of ephemeral nodes held in ZooKeeper.
Ephemeral Node,node
clickhouse_GlobalThread

Number of threads in global thread pool.
Global Thread,thread
clickhouse_GlobalThreadActive

Number of threads in the global thread pool running a task.
Global Thread Active,thread
clickhouse_HTTPConnection

Number of connections to HTTP server
HTTP Connection,connection
clickhouse_InterserverConnection

Number of connections from other replicas to fetch parts
Interserver Connection,connection
clickhouse_LocalThread

Number of threads in local thread pools. The threads in local thread pools are taken from the global thread pool.
Local Thread,thread
clickhouse_LocalThreadActive

Number of threads in local thread pools running a task.
Local Thread Active,thread
clickhouse_MMappedFileBytes

Sum size of mmapped file regions.
MMapped File Bytes
clickhouse_MMappedFiles

Total number of mmapped files.
MMapped Files
clickhouse_MaxDDLEntryID

Max processed the DDL entry of DDLWorker.
MaxDDL Entry ID
clickhouse_MemoryTracking

Total amount of memory (bytes) allocated by the server.
Memory Tracking,byte
clickhouse_Systemmetric_Merge

Number of executing background merges
Systemmetric Merge,merge
clickhouse_MySQLConnection

Number of client connections using MySQL protocol
My SQL Connection,connection
clickhouse_NetworkReceive

Number of threads receiving data from the network. Only ClickHouse-related network interaction is included, not by 3rd party libraries.
Network Receive
clickhouse_NetworkSend

Number of threads sending data to the network. Only ClickHouse-related network interaction is included, not by 3rd party libraries.
Network Send
clickhouse_OpenFileForRead

Number of files open for reading
Open File For Read,file
clickhouse_OpenFileForWrite

Number of files open for writing
Open File For Write,file
clickhouse_PartMutation

Number of mutations (ALTER DELETE/UPDATE)
Part Mutation
clickhouse_PartsCommitted

Active data part, used by current and upcoming SELECTs.
Parts Committed
clickhouse_PartsCompact

Compact parts
Parts Compact
clickhouse_PartsDeleteOnDestroy

Part was moved to another disk and should be deleted in its own destructor.
Parts Delete On Destroy
clickhouse_PartsDeleting

Not active data part with identity refcounter, it is deleting right now by a cleaner
Parts Deleting
clickhouse_PartsInMemory

In-memory parts
Parts In Memory
clickhouse_PartsOutdated

Not active data part, but could be used by only current SELECTs, could be deleted after SELECTs finishes.
Parts Outdated
clickhouse_PartsPreCommitted

The part is in data_parts, but not used for SELECTs
Parts Pre Committed
clickhouse_PartsTemporary

The part is generated now, it is not in the data_parts list.
Parts Temporary
clickhouse_PartsWide

Wide parts.
Parts Wide
clickhouse_PostgreSQLConnection

Number of client connections using PostgreSQL protocol
Postgre SQL Connection,connection
clickhouse_Systemmetric_Query

Number of executing queries
Systemmetric Query,query
clickhouse_QueryPreempted

Number of queries that are stopped and waiting due to 'priority' setting.
Query Preempted,query
clickhouse_QueryThread

Number of query processing threads
Query Thread,thread
clickhouse_RWLockActiveReaders

Number of threads holding read lock in a table RWLock.
RWLock Active Readers,thread
clickhouse_RWLockActiveWriters

Number of threads holding write lock in a table RWLock.
RWLock Active Writers,thread
clickhouse_RWLockWaitingReaders

Number of threads waiting to be read on a table RWLock.
RWLock Waiting Readers,thread
clickhouse_RWLockWaitingWriters

Number of threads waiting to write on a table RWLock.
RWLock Waiting Writers,thread
clickhouse_Read

Number of read (read, pread, io_getevents, etc.) syscalls in fly
Read,read
clickhouse_ReadonlyReplica

Number of Replicated tables that are currently in readonly state due to re-initialization after ZooKeeper session loss or due to startup without ZooKeeper configured.
Read only Replica,table
clickhouse_ReplicatedChecks

Number of data parts checking for consistency
Replicated Checks
clickhouse_ReplicatedFetch

Number of data parts being fetched from replica
Replicated Fetch
clickhouse_ReplicatedSend

Number of data parts being sent to replicas
Replicated Send
clickhouse_SendExternalTables

Number of connections that are sending data for external tables to remote servers. External tables are used to implement GLOBAL IN and GLOBAL JOIN operators with distributed subqueries.
Send External Tables,connection
clickhouse_SendScalars

Number of connections that are sending data for scalars to remote servers.
Send Scalars,connection
clickhouse_StorageBufferBytes

Number of bytes in buffers of Buffer tables.
Storage Buffer Bytes,byte
clickhouse_StorageBufferRows

Number of rows in buffers of Buffer tables.
Storage Buffer Rows,row
clickhouse_SyncDrainedConnections

Number of connections drained synchronously.
Sync Drained Connections,connection
clickhouse_TCPConnection

Number of connections to TCP server (clients with native interface), also included server-server distributed query connections.
TCP Connection,connection
clickhouse_TablesToDropQueueSize

Number of dropped tables that are waiting for background data removal.
Tables To Drop Queue Size,table
clickhouse_Write

Number of write (write, pwrite, io_getevents, etc.) syscalls in fly.
Write,write
clickhouse_ZooKeeperRequest

Number of requests to ZooKeeper in fly.
ZooKeeper Request,request
clickhouse_ZooKeeperSession

Number of sessions (connections) to ZooKeeper. Should be no more than one, because using more than one connection to ZooKeeper may lead to bugs due to lack of linearizability (stale reads) that ZooKeeper consistency model allows.
ZooKeeper Session,connection
clickhouse_ZooKeeperWatch

Number of watches (event subscriptions) in ZooKeeper.
ZooKeeper Watch
clickhouse_CompressedReadBufferBytes_per_sec

Number of uncompressed bytes (the number of bytes after decompression) read from compressed sources (files, network).
Compressed Read Buffer Bytes,bytes/sec
clickhouse_ContextLock_per_sec

Number of times the lock of Context was acquired or tried to acquire. This is a global lock.
Context Lock
clickhouse_DiskReadElapsedMicroseconds

Total time spent waiting to read syscall. This includes reads from page cache.
Disk Read Elapsed Microseconds
clickhouse_CannotWriteToWriteBufferDiscard_per_sec

Number of stack traces dropped by query profiler or signal handler because pipe is full or cannot write to pipe.
Cannot Write To Write Buffer Discard
clickhouse_CompressedReadBufferBlocks_per_sec

Number of compressed blocks (the blocks of data that are compressed independent of each other) read from compressed sources (files, network).
Compressed Read Buffer Blocks,blocks/sec
clickhouse_DiskWriteElapsedMicroseconds

Total time spent waiting to write syscall. This includes writes to page cache.
Disk Write Elapsed Microseconds
clickhouse_FileOpen_per_sec

Number of files opened.
File Open,files/sec
clickhouse_InsertedBytes_per_sec

Number of bytes (uncompressed; for columns as they are stored in memory) INSERTed to all tables.
Inserted Bytes,bytes/sec
clickhouse_InsertedRows_per_sec

Number of blocks INSERTed to MergeTree tables. Each block forms a data part of level zero.
Merge Tree Data Writer Blocks,blocks/sec
clickhouse_MergeTreeDataWriterBlocksAlreadySorted_per_sec

Number of blocks INSERTed to MergeTree tables that appeared to be already sorted.
Merge Tree Data Writer Blocks Already Sorted,blocks/sec
clickhouse_MergeTreeDataWriterCompressedBytes_per_sec

Bytes written to filesystem for data INSERTed to MergeTree tables.
Merge Tree Data Writer Compressed Bytes,bytes/sec
clickhouse_MergeTreeDataWriterRows_per_sec

Number of rows INSERTed to MergeTree tables.
Merge Tree Data Writer Rows,rows/sec
clickhouse_MergeTreeDataWriterUncompressedBytes_per_sec

Uncompressed bytes (for columns as they are stored in memory) INSERTed to MergeTree tables.
Merge Tree Data Writer Uncompressed Bytes,bytes/sec
clickhouse_MergedRows_per_sec

Rows read for background merges. This is the number of rows before merge.
Merged Rows,rows/sec
clickhouse_MergedUncompressedBytes_per_sec

Uncompressed bytes (for columns as they are stored in memory) that were read for background merges. This is the number before merge.
Merged Uncompressed Bytes,bytes/sec
clickhouse_MergesTimeMilliseconds

Total time spent for background merges.
Merges Time Milliseconds
clickhouse_NetworkReceiveBytes_per_se

Total number of bytes received from network. Only ClickHouse-related network interaction is included, not by 3rd party libraries.
Network Receive Bytes,bytes/sec
clickhouse_NetworkSendBytes_per_sec

Total number of bytes sent to the network. Only ClickHouse-related network interaction is included, not by 3rd party libraries.
Network Send Bytes,bytes/sec
clickhouse_NetworkSendElapsedMicroseconds

Total time spent waiting for data to send to network or sending data to network. Only ClickHouse-related network interaction is included, not by 3rd party libraries
Network Send Elapsed Microseconds,microsecond
clickhouse_NetworkReceiveElapsedMicroseconds

Total time spent waiting for data to receive or receiving data from the network. Only ClickHouse-related network interaction is included, not by 3rd party libraries
Network Receive Elapsed Microseconds,microsecond
clickhouse_OSCPUVirtualTimeMicroseconds

CPU time spent seen by OS. Does not include involuntary waits due to virtualization.
OSCPU Virtual Time Microseconds,microsecond
clickhouse_OSCPUWaitMicroseconds

Total time a thread was ready for execution but waiting to be scheduled by OS, from the OS point of view.
OSCPU Wait Microseconds,microsecond
clickhouse_OSReadBytes_per_sec

Number of bytes read from disks or block devices. Doesn't include bytes read from page cache. May include excessive data due to block size, readahead, etc.
OS Read Bytes,bytes/sec
clickhouse_OSReadChars_per_sec

Number of bytes read from filesystem, including page cache.
OS Read Chars,bytes/sec
clickhouse_OSWriteBytes_per_sec

Number of bytes written to disks or block devices. Doesn't include bytes that are in page cache dirty pages. May not include data that was written by the OS asynchronously.
OS Write Bytes,bytes/sec
clickhouse_OSWriteChars_per_sec

Number of bytes written to filesystem, including page cache.
OS Write Chars,bytes/sec
clickhouse_Systemevent_Query_per_sec

Number of queries to be interpreted and potentially executed. Does not include queries that failed to parse or were rejected due to AST size limits, quota limits or limits on the number of simultaneously running queries. May include internal queries initiated by ClickHouse itself. Does not count subqueries.
Systemevent Query,query/sec
clickhouse_QueryTimeMicroseconds_per_sec

Total time of all queries.
Query Time Microseconds,microsecond
clickhouse_ReadBufferFromFileDescriptorRead_per_sec

Number of reads (read/pread) from a file descriptor. Does not include sockets.
Read Buffer From File Descriptor Read,reads/sec
clickhouse_ReadBufferFromFileDescriptorReadBytes_per_sec

Number of bytes read from file descriptors. If the file is compressed, this will show the compressed data size.
Read Buffer From File Descriptor Read Bytes,bytes/sec
clickhouse_ReadCompressedBytes_per_sec

Number of bytes (the number of bytes before decompression) read from compressed sources (files, network).
Read Compressed Bytes,bytes/sec
clickhouse_RealTimeMicroseconds

Total (wall clock) time spent in processing (queries and other tasks) threads (not that this is a sum).
Real Time Microseconds,microsecond
clickhouse_RegexpCreated_per_sec

Compiled regular expressions. Identical regular expressions compiled just once and cached forever.
Regexp Created
clickhouse_SelectQuery_per_sec

Same as Query, but only for SELECT queries
Select Query,query/sec
clickhouse_SelectQueryTimeMicroseconds

Total time of SELECT queries
Select Query Time Microseconds,microsecond
clickhouse_SelectedBytes_per_sec

Number of bytes (uncompressed; for columns as they are stored in memory) SELECTed from all tables.
Selected Bytes,bytes/sec
clickhouse_SelectedRows_per_sec

Number of rows SELECTed from all tables.
Selected Rows,rows/sec
clickhouse_SystemTimeMicroseconds

Total time spent in processing (queries and other tasks) threads executing CPU instructions in OS kernel space. This includes the time the CPU pipeline stalled due to cache misses, branch mispredictions, hyper-threading, etc.
System Time Microseconds,microsecond
clickhouse_UserTimeMicroseconds

Total time spent in processing (queries and other tasks) threads executing CPU instructions in user space. This include time CPU pipeline was stalled due to cache misses, branch mispredictions, hyper-threading, etc
User Time Microseconds,microsecond
clickhouse_WriteBufferFromFileDescriptorWrite_per_sec

Number of writes (write/pwrite) to a file descriptor. Does not include sockets.
Write Buffer From File Descriptor Write,writes/sec
clickhouse_WriteBufferFromFileDescriptorWriteBytes_per_sec

Number of bytes written to file descriptors. If the file is compressed, this will show compressed data size.
Write Buffer From File Descriptor Write Bytes,bytes/sec
clickhouse_CompiledExpressionCacheCount

This metric will be renamed in a future minor release.
Compiled Expression Cache Count
clickhouse_MarkCacheBytes

The size of the cache of `marks` for StorageMergeTree.
Mark Cache Bytes,byte
clickhouse_MarkCacheFiles

This metric will be renamed in a future minor release.
Mark Cache Files
clickhouse_MaxPartCountForPartition

The maximum number of active parts in partitions.
Max Part Count For Partition
clickhouse_NumberOfDatabases

The current number of databases.
Number Of Databases
clickhouse_NumberOfTables

The current number of tables.
Number Of Tables,table
clickhouse_ReplicasMaxAbsoluteDelay

The maximum replica queue delay relative to current time.
Replicas Max Absolute Delay,millisecond
clickhouse_ReplicasMaxInsertsInQueue

This metric will be renamed in a future minor release.
Replicas Max Inserts In Queue
clickhouse_ReplicasMaxMergesInQueue

This metric will be renamed in a future minor release.
Replicas Max Merges In Queue
clickhouse_ReplicasMaxQueueSize

This metric will be renamed in a future minor release.
Replicas Max Queue Size,millisecond
clickhouse_ReplicasSumInsertsInQueue

This metric will be renamed in a future minor release.
Replicas Sum Inserts In Queue
clickhouse_ReplicasSumMergesInQueue

This metric will be renamed in a future minor release.
Replicas Sum Merges In Queue
clickhouse_ReplicasSumQueueSize

The number of replication tasks in queue.
Replicas Sum Queue Size,task
clickhouse_UncompressedCacheBytes

This metric will be renamed in a future minor release.
Uncompressed Cache Bytes,byte
clickhouse_UncompressedCacheCells

This metric will be renamed in a future minor release.
Uncompressed Cache Cells
clickhouse_Uptime

The amount of time ClickHouse has been active.
Uptime,second
Clickhouse_jemalloc_active

This metric will be renamed in a future minor release.
Jemalloc Active,byte
Clickhouse_jemalloc_allocated

The amount of memory allocated by ClickHouse.
Jemalloc Allocated,byte
Clickhouse_jemalloc_background_thread_num_runs

This metric will be renamed in a future minor release.
Jemalloc Background Thread Num Runs,byte
Clickhouse_jemalloc_background_thread_num_threads

This metric will be renamed in a future minor release.
Jemalloc Background Thread Num Threads,thread
Clickhouse_jemalloc_background_thread_run_intervals

This metric will be renamed in a future minor release.
Jemalloc Background Thread Run Intervals,byte
Clickhouse_jemalloc_mapped

The amount of memory in active extents mapped by the allocator.
Jemalloc Mapped,byte
Clickhouse_jemalloc_metadata

The amount of memory dedicated to metadata, which comprise base allocations used for bootstrap-sensitive allocator metadata structures and internal allocations.
Jemalloc Metadata,byte
Clickhouse_jemalloc_metadata_thp

This metric will be renamed in a future minor release.
Jemalloc Metadatathp,byte
Clickhouse_jemalloc_resident

The amount of memory in physically resident data pages mapped by the allocator, comprising all pages dedicated to allocator metadata, pages backing active allocations, and unused dirty pages.
Jemalloc Resident,byte
Clickhouse_jemalloc_retained

he amount of memory in virtual memory mappings that were retained rather than being returned to the operating system.
Jemalloc Retained,byte
clickhouse_S3ReadBytes_per_sec

Total read bytes (incoming) in GET and HEAD requests to S3 storage.
S3 Read Bytes,bytes/sec
clickhouse_S3ReadMicroseconds

Time of GET and HEAD requests to S3 storage
S3 Read Microseconds,microsecond
clickhouse_S3ReadRequestsCount_per_sec

Number of GET and HEAD requests to S3 storage.
S3 Read Requests Count,requests/sec
clickhouse_S3WriteBytes_per_sec

Total write bytes (outgoing) in POST, DELETE, PUT and PATCH requests to S3 storage.
S3 Write Bytes,bytes/sec
clickhouse_S3WriteMicroseconds_per_sec

Time of POST, DELETE, PUT and PATCH requests to S3 storage.
S3 Write Microseconds,microsecond
clickhouse_S3WriteRequestsCount_per_sec

Number of POST, DELETE, PUT and PATCH requests to S3 storage.
S3 Write Requests Count,requests/sec
clickhouse_S3WriteRequestsErrors_per_sec

Number of non-throttling errors in POST, DELETE, PUT and PATCH requests to S3 storage.
S3 Write Requests Errors,errors/sec
clickhouse_MergeTreeDataProjectionWriterBlocks_per_sec

Number of blocks INSERTed to MergeTree tables projection. Each block forms a data part of level zero.
Merge Tree Data Projection Writer Blocks,blocks/sec
clickhouse_MergeTreeDataProjectionWriterCompressedBytes_per_sec

Number of blocks INSERTed to MergeTree tables projection that appeared to be already sorted.
Merge Tree Data Projection Writer Compressed Bytes,blocks/sec
clickhouse_MergeTreeDataProjectionWriterRows_per_sec

Number of rows INSERTed to MergeTree tables projection.
Merge Tree Data Projection Writer Rows,rows/sec
clickhouse_MergeTreeDataProjectionWriterUncompressedBytes_per_sec

Uncompressed bytes (for columns as they are stored in memory) INSERTed to MergeTree tables projection.
Merge Tree Data Projection Writer Uncompressed Bytes,bytes/sec
clickhouse_MergeTreeDataProjectionWriterBlocksAlreadySorted_per_sec

Total number of blocks INSERTed to MergeTree tables projection that appeared to be already sorted.
Merge Tree Data Projection Writer Blocks Already Sorted,blocks/sec
clickhouse_LeaderElectionAcquiredLeadership_per_sec

Number of times a ReplicatedMergeTree table became a leader. Leader replica is responsible for assigning merges, cleaning old blocks for deduplications and a few more bookkeeping tasks.
Leader Election Acquired Leadership
clickhouse_CannotRemoveEphemeralNode_per_sec

Number of times an error happened while trying to remove an ephemeral node. This is not an issue, because our implementation of ZooKeeper library guarantees that the session will expire and the node will be removed.
Cannot Remove Ephemeral Node,errors/sec
clickhouse_BackgroundPoolTask

Number of active tasks in BackgroundProcessingPool (merges, mutations, fetches, or replication queue bookkeeping)
Background Pool Task,task
clickhouse_LeaderElection

Number of Replicas participating in leader election. Equals the total number of replicas in usual cases.
Leader Election,shard
clickhouse_LeaderReplica

Number of Replicated tables that are leaders. Leader replica is responsible for assigning merges, cleaning old blocks for deduplications and a few more bookkeeping tasks. There may be no more than one leader across all replicas at one moment of time. If there is no leader it will be elected soon or it indicates an issue.
Leader Replica,table
clickhouse_MemoryTrackingForMerges

Total amount of memory (bytes) allocated for background merges. Included in MemoryTrackingInBackgroundProcessingPool.
Memory Tracking For Merges,byte
clickhouse_MemoryTrackingInBackgroundMoveProcessingPool

Total amount of memory (bytes) allocated in the background processing pool (that is dedicated for background moves).
Memory Tracking In Background Move Processing Pool,byte
clickhouse_MemoryTrackingInBackgroundProcessingPool

Total amount of memory (bytes) allocated in the background processing pool (that is dedicated for background merges, mutations and fetches).
Memory Tracking In Background Processing Pool,byte
clickhouse_MemoryTrackingInBackgroundSchedulePool

Total amount of memory (bytes) allocated in the background schedule pool (that is dedicated for bookkeeping tasks of Replicated tables).
Memory Tracking In Background Schedule Pool,byte